#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main() {
    int n;
    long long int sum = 0;
    long long int ans = 1;
    scanf("%d", &n);
    if (n == 1)
        printf("1");
    else {
        for (int i = n; i > 1; i = i - 2) {
            sum = i * (i - 1);
            ans = ans * sum;
        }
        printf("%lld", ans);
    }

}